Connections: Manure Universe

Sally Brown

Sally Brown
BioCycle May 2014, Vol. 55, No. 4, p. 45

I had fish for dinner tonight and was meatless yesterday too. I am not a vegetarian. However, I’ve just had to compile information on animal manure in the U.S. That was enough to make cabbage and potatoes sound like a delicious alternative to prime rib. Much of the discussion on residuals and composting has been centered on urban residuals. Yard trimmings, food scraps and municipal biosolids all fall into this category. Composting of these materials is typically highly regulated with permits required from at least one if not several municipal and state agencies.

Direct land application prior to composting is an option for biosolids but not much else. If the biosolids don’t fall into the category of “Class A” or pathogen free materials, their use is tightly regulated and in some instances, is outright prohibited. In many cases, public acceptance of these materials or of sites to process these materials is tenuous at best, outright hostile at worst. And all this is happening while right next to us, there is this alternative universe of animal manure management.

Animal manures, like urban residuals, can make terrific soil amendments. Most are high in both carbon and nutrients. Most provide a slow release fertilizer as well as a soil conditioner to agricultural fields. I would be happy to tout their benefits, much as I do the benefits of urban residuals. But there are also significant concerns about animal manures- mostly related to inappropriate regulation and as a consequence, improper use or lack of use with associated environmental and public health consequences. And while there aren’t enough urban residuals to go around (about enough biosolids and municipal organics compost to cover 1% of arable land), there is enough manure to make more than a dent.

How Much?

Animals raised in significant quantities include hogs for meat, cattle for meat and dairy, and chickens for eggs and meat. While chickens are small (about 2 lbs for broilers and 4 lbs for layers) and only produce small amounts of manure (0.2 and 0.14 lbs per bird per day respectively), hogs are about as big as people and a lot more productive (3 to 4.2 lbs of manure/day). Each cow is like a family — weighing between 500 to 1,200 lbs and producing anywhere from 43 to 90 lbs of manure each day.

And then you have to consider populations. If you think Manhattan is too crowded, don’t go near an animal facility. Nationwide, 9 million dairy cows, 26 million beef cows, 120 million hogs, 292 million layers (chickens for eggs), and 8.6 billion broilers (chicken for meat) are raised. If you multiply the average manure production by the number of animals you get the part of the story that is pertinent to the organics recycling industry: Over 400 million wet tons of cow manure, about 300 million wet tons of swine manure and 220 million wet tons of poultry manure. If at this point, any of you would like my recipe for cabbage and potatoes, just send me an email.

Finally, just as people are moving to cities, animals are increasingly raised in the equivalent of cities — facilities that house large numbers of animals in a small area. While this may make production more efficient, it also makes manure disposal or beneficial use more challenging. Different regions of the U.S. specialize in raising different types of animals. If you want to plan tours, five states — Georgia, Alaska, Alabama, Missouri and North Carolina — raise more than 60 percent of the birds in the U.S. If pigs are your thing, the majority of hogs are raised in the Midwest and North Carolina. And if you think wine and cheese make an ideal combination, head to California, which has the single largest concentration of dairy cows (1.78 million). If beef is what’s for dinner then you’ll have your best chance of spotting cattle in Texas, Nebraska, Kansas, California or Oklahoma, where over 50 percent of the total population is housed. Actually, you can have a wonderful time in California starting with wine and cheese and moving on to steak or boeuf bourguignon for a main course. All of this in a state where many counties have banned land application of biosolids.

Manure Utilization

Manures are a resource based on their nutrient and carbon contents. When applied properly, studies have shown plant and soil benefits when substituted for synthetic fertilizers (Fronning et al., 2008; Shrestha et al., 2013). When stored for too long or over applied, a range of problems occur including fugitive gas emissions and excessive nutrient loading. Manures also contain their share of contaminants. Metal concentrations (with the exception of lead) are typically about the same in manures as they are in municipal biosolids. In some cases, manures can have much higher levels, for example the concentrations of arsenic in chicken manure.

Manures are also loaded with their share of pharmaceuticals. Many animals are preventatively dosed with antibiotics. Soils that have received heavy manure applications can show increased antibiotic resistance. Finally, the pathogens present in manures have repeatedly made their way into food crops. Pathogen tainted foodstuffs, most famously by E Coli 157, have sickened and killed many people.

Here is the concern. Manures are often not used in a manner that will provide optimal benefits and assure public safety. It costs more money to use manures in comparison to synthetic fertilizers. It also costs money, lots more money, to treat manures to reduce pathogen populations and potentially mineralize antibiotics. And in most states, manure managers are not subject to the same level of oversight and regulation that effectively provide a cost incentive to use and treat these materials in a manner that is protective of both public health and the environment. In Oklahoma, for example — home to a lot of cows and chickens — the primary concern with manure management is protection of water resources. Rather than penalties and regulatory oversight, manure managers are governed by educational outreach and voluntary compliance.

Composting is an obvious way to reduce any potential hazards associated with pathogens, nutrients and even antibiotics in animal manures. Studies have also shown some increased benefits associated with applying composted manures to soils in comparison to application of raw manures (Fronning et al., 2008; Ryals and Silver, 2013, Ryals et al., 2014; Shrestha et al., 2013). These benefits are mostly related to reduced fugitive emissions. Composting costs money though, more money than applying untreated manure even if it requires transport to significant distances from animal production sites. There have to be some incentives to incur that extra cost. Is there the political will to start applying the very same permit requirements and regulations to animal manure operations that are bestowed upon biosolids and composting of municipal organics?

In the absence of that will, anyone have any vegetarian recipes to share?

Sally Brown is a Research Associate Professor at the University of Washington in Seattle and a member of BioCycle’s Editorial Board. Part I of this article, “Compost And Mulch Aid Drought Survival,” appeared in the March/April 2014 issue.

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